1. Field of the Invention
The present invention relates to a fluid meter, in particular a water meter with a volumetric measurement chamber.
2. Description of the Prior Art
A prior art meter of this kind comprises a casing or tank having an inlet pipe and an outlet pipe and into which is inserted an oscillating piston type volumetric measurement chamber. The measurement chamber has at least one inlet orifice and at least one outlet orifice. This kind of meter is well known to the person skilled in the art.
In some forms of measurement chamber, like that shown in FIG. 1, the inlet orifice or the outlet orifice 5 extends over a particular height on the lateral wall of the enclosure of the chamber 1. This orifice must be connected in a sealed manner to the corresponding inlet or outlet pipe 3, 4 and, to this end, a seal 6 is fitted into a groove around the orifice on the external face of the enclosure of the chamber. Once the measurement chamber 1 has been inserted into the tank 2, this seal 6 is compressed in the gap between the measurement chamber and the tank and provides a sealed passage for the fluid between the corresponding pipe and the orifice.
The measurement chamber 1 has a cylindrical external surface of generally constant circular section, except at the place where the seal is secured, and likewise the internal surface of the tank 2. This is known in the art. The shape of the seal 6 corresponds to that of the orifice, which is generally rectangular.
Assembly is effected by fitting the seal into its groove in the measurement chamber 1 and then inserting the measurement chamber into the tank 2.
To provide a seal, the unstressed seal has a diameter greater than the width of the gap between the measurement chamber and the tank. Thus when the measurement chamber, which has a constant generally circular section, is inserted, the seal is subjected to forces in the direction opposite to that in which the measurement chamber is inserted into the tank, which is also of constant circular section, and this applies over the whole of the assembly height. These relatively high forces may expel the seal from the groove, detaching the seal from the measurement chamber, with the risk of deforming the seal in a direction opposite to the insertion direction, and even cutting the seal, the measurement chamber being assembled to the tank with no seal, making the meter useless. These problems are incompatible with mass production assembly of the meter.